Magnesium research set to inform preterm care

Giving magnesium to mothers just before early birth, at 30 to 34 weeks, may help babies’ brains develop, but more research is needed.

Professor Caroline Crowther.
Professor Caroline Crowther's study found no advantage for survival and cerebral palsy with magnesium, but pooled with earlier studies, benefits emerge.

Care for mothers and preterm babies is set to be improved by new research on giving magnesium sulphate just before birth.

“We have known for 14 years that magnesium sulphate given just prior to very early birth, before 30 weeks’ gestation, is beneficial for the child's development, and is now recommended practice” study lead Professor Crowther of the University of Auckland’s Liggins Institute says.

“What we don’t know is whether there is a similar advantage to administering magnesium sulphate at 30 to 34 weeks, which is still considered early.”

The Liggins research team, in collaboration with the IMPACT Clinical Trials Network of the Perinatal Society of Australia and New Zealand, recruited 1433 mothers and their 1679 babies into the trial, from 24 hospitals across New Zealand and Australia.

The mothers were randomised to receive either magnesium sulphate or a saline control as an intravenous solution shortly before birth at 30 to 34 weeks’ gestation.

The study, including a follow-up developmental assessment when the babies were two years old and known as ‘Magenta’, took place from 2012 to 2021. See JAMA.

Overall, the chances of the child surviving without cerebral palsy at two years of age were similar whether their mother received magnesium sulphate or the saline placebo (97.2% versus 97.6%).

The health of the child at two years was also similar, according to assessments for sight, hearing, language and cognitive development, height and weight.

However, there was a reduction in breathing difficulties (34% versus 41%) and use of oxygen long-term (5.6% versus 8.2%) in newborn babies whose mothers received magnesium sulphate. There was some suggestion children whose mothers were given magnesium sulphate may have more behavioural problems (10% versus 6%), but this will require further later follow up.

When the Magenta results are examined together with the earlier studies using magnesium sulphate before preterm birth the findings are similar, says Professor Crowther.

One thing the Liggins researchers plan to do is pool individuals’ data from Magenta with those from earlier studies to get summary information from a much larger number of mothers and babies to see if health benefits are seen at these higher gestations, particularly for cerebral palsy, and also to assess the best dose to use.

Importantly, the Magenta study found no significant harm to mothers receiving the intravenous magnesium sulphate at 30 to 34 weeks.

These findings provide helpful evidence that will help guide care of mothers at risk of preterm birth at 30 to 34 weeks’ gestation, says Liggins director Professor Justin O’Sullivan.

“The results will be available to healthcare providers caring for mothers and their babies and will be used to update the clinical guidelines for New Zealand and Australia,” Professor O’Sullivan says.

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